The immune system is the first line of defense against many pathologies. Particularly, the lymphoid compartment is concerned with monitoring tumorigenesis, invasion by pathogens, such as bacteria and viruses, aiding in the removal of foreign bodies, and the like. Essential to the ability of the lymphoid compartment to protect the host against the various pathologies is the ability to recognize self from non-self. In monitoring tumorigenesis, subtle distinctions may be involved and the high incidence of cancer, particularly in the aged, suggests that the monitoring frequently breaks down over time. In addition, because of the enormous diversity of the environment to which the immune system is exposed, there is always the possibility that epitopes will be encountered, which may trigger an immune response which can be directed against self. Other mechanisms may also be operative in the process where a lymphoid cell attacks an endogenous epitope. These autoimmune diseases can be extremely destructive, as is evidenced by diabetes, rheumatoid arthritis, neuronal diseases, such as multiple sclerosis, and the like. While in many cases, the disease is associated with T-cell attack, in some of the diseases, there may be a B-cell component, and in other diseases, such as rheumatoid arthritis and lupus nephritis, the primary mediator may be B-cells.
The lymphoid compartment may be more susceptible than other cells to tumorigenesis, because of the recombinatorial processes associated with the rearrangements involved with formation of immunoglobulins and the T-cell receptor. Lymphoid cancers, such as lymphomas and leukemias are particularly dangerous, because of the opportunity for migration of the lymphoid cells throughout the body and the many sites in the periphery, where lymphocytes reside, so as to provide numerous opportunities for metastasis. Furthermore, these diseases interfere with the native process which is intended to monitor tumorigenesis.
There is, therefore, substantial interest in being able to develop techniques and therapies which will allow for selective reduction in cell types associated with pathogenesis.